What mommas are returning to work full time after maternity leave?

I'm so lost right now ... I was thinking about going down to part time after maternity leave. This will be my first child. I'm a registered nurse and 25 years old. I'm 21 weeks now and I was just blind sided with a promotion to be the nurse manager for my clinic. Part of me feels guilty for being excited about this. I would need to work at least 4 days a week with this promotion so going part time is probably out of the question. Am I being a bad mom for putting my career first right now? I feel like if I pass this up I may not get another opportunity later on. I did put myself through a crazy amount of stress to finish nursing school it would be ashame to kinda give up on my career. Any thoughts? Additional info: I work for a private practice so I'm off on weekends and holidays.